I've used 1/2 whisper for my filtration on my super-stocked 55 gallon, and it's been superb. In fact, I dumped my walmart knockoff emperor filter for a second whisper so I could finally get rid of carbon. (It's near impossible cutting the carbon out of one of those wal-mart "penguin filters").
The whispers come with a foam square, as mentioned above, and the biobag, which is basically a polyester batting mesh envelope that you can stuff with carbon, more batting, peat, Chiapets, whatever.
Where I live Aquaclears are not sold and the only options available are Whisper (cheap) and Penguins.